Camshaft adjusters are used to alter the control times for the opening or closing of valves. The fixed angular relationship between the camshaft and the crankshaft which drives it is eliminated and the control times can be optimally set as a function of the rev speed and further parameters. Camshaft adjusters allow the camshaft to be twisted relative to the crankshaft.
Known vane-type camshaft adjusters have a rotor comprised of a plurality of radially protruding blades, which are urged by the force of a spring radially outward against a stator housing. A plurality of stops projecting radially inward are formed on the stator and limit the adjustment movement of the rotor in both rotational directions when the blades run against the stops. The blades bear against the stator with their leading edges, so that between, respectively, a blade side and the adjacent side of a stop of the stator, a chamber is formed, into which a fluid, generally the engine oil, is fed via a valve assigned to the camshaft adjuster. The stator serves, on the one hand, to separate and seal the fluid chambers, on the other hand to fix the angle of adjustment between the camshaft and the crankshaft.
The torque transmitted to the rotor rests, via the blades inserted in grooves, against the stator and, hydraulically, against the oil pad in the stator chambers. The force which thereby acts upon the blades engenders, for its part, reaction forces in the groove of the rotor. A force acts upon the groove edge on the external diameter of the rotor, the associated reaction force acts upon the opposite groove side in the groove bottom. These forces produce a combined tensile and flexural load in the two transitions between the groove side face and the groove bottom. In the corner region at the transition between the groove side face and the groove bottom, a dynamically generated stress concentration is produced by the notch effect. For this reason, the transition region, in conventional vane-type camshaft adjusters, is of rounded configuration, so that it undercuts the groove side face. However, considerable stresses still are generated in the corner region, which, under the usual operating loads, can be critical to the materials used.